refactor: apply clippy auto-fixes (162 warnings resolved)

- Fix needless borrows and references
- Collapse nested if statements
- Replace manual strip_prefix with str::strip_prefix()
- Remove redundant closures in map/unwrap_or_else
- Use Iterator::next_back() instead of rev().next()
- Simplify map_or patterns
- Use std::io::Error::other() instead of new(ErrorKind::Other, ..)
- Use div_ceil() instead of manual ceiling division
- Consolidate format! string arguments
- Various other idiomatic Rust improvements

39 files changed, 220 insertions(+), 320 deletions(-)

src/infrastructure/db.rs

@@ -73,8 +73,7 @@ pub async fn create_database_pool(config: &AppConfig) -> Result<PgPool> {
 async fn tables_exist(pool: &PgPool) -> bool {
     sqlx::query("SELECT EXISTS (SELECT 1 FROM pg_tables WHERE schemaname = 'auth' AND tablename = 'users')")
         .fetch_one(pool)
-        .await
-        .and_then(|row| Ok(row.get::<bool, _>(0)))
+        .await.map(|row| row.get::<bool, _>(0))
         .unwrap_or(false)
 }